Glow plug failures cured with new bearings - why?

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BobBonahoom

Well-Known Member
Joined
Mar 6, 2009
Messages
532
I have found over the years that when an engine that otherwise does not blow glow plugs, starts blowing plugs, it may be a sign of bad bearings. When I change bearings the plug failures usually stop. Does anybody know why or how bearings affect glow plugs???
 
Bob,

Its usually because it causes a lean run. The bearings clearances! And maybe even debri from the bearing.

Thats the way I understand it, There is probably other reasons, maybe excessive load/heat.
 
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If the chrome comes off your balls it can pepper the plug with debris.
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I have found over the years that when an engine that otherwise does not blow glow plugs, starts blowing plugs, it may be a sign of bad bearings. When I change bearings the plug failures usually stop. Does anybody know why or how bearings affect glow plugs???
Bobwhen bearings start going bad, the labryth seal starts leaking allowing the crank case presure to fluctuate and the engine to go super lean, which eats the plugs causeing damage to the engine.

JM2CW

Moby
 
I've been told that microscopic bits of chrome come off the bearings when they're going bad and when they come in contact with glow plug coil, create a hot spot and break coil. This can happen up inside the plug. That's why plug quite often looks good, but won't glow.
 
If it is the chrome bits coming off the bearings that take out the glow plug, that means the piston/liner fit will be gone too.
 
All this seems to argue for replacing the bearings based on running time rather than waiting for a failure. Glenn Quarles told me that he replaces bearings every few months in his engines. Although that seems expensive, at $5 per glow plug for each failure, plus the cost of piston/sleeves and crankcases with a bad seal, it may be well worth it. I wonder if it makes sense to pay more and use ceramic rear bearings with no chrome and just replace the front bearings on a regular basis? If chrome is coming off the race in addition to the balls, ceramic may be no better. It would be interesting to hear from some bearing experts on all this.
 
Bob.. I've done the ceramics thing from having Gregs bearings( phenomenal) to factory replacements... top end?.. maybe... just that little extra was there earlier in some of my engines... your idea of steel front is key there IMO because that poor little 607 takes the brunt of punishment from the prop and flexshaft in todays installs...( trend of the square drive coming back).. Ceramics.. do not like all synthetic fuel blends... in my testing.. a lean run will be a failure as theres nothing to little left to lubricate the system... they dont like rough water punishment in my travels either... and.... lastly.... when they fracture( lean, over rev situation...) its normally a half ball gets thrown through the engine and plants in the button and smashes all around rather nicely... pick your poison accordingly... but... additional castor is your friend... now... as for steel, i only replace with factory OEM in my novas and i keep 607s on hand replaceing them frequently... ive testing days i wont beat hell out of engines on bad water for that fact especially... Nitro... is the ultimate oxidizer... and IMO that means rust and wear very quickly after it contacts metals... again that means bearing wear possibly and future failure... catastrophic if youre not diligent... as posted i will notice an engine dinging plugs without my finger on the 3rd channel, and youll see the flakes on the face sometimes or itll break the element inoordinately.. im looking at the plug every test run anyway, right?.. and itll show up... that engine... is on the bench.. awaiting bearings... while i dont necessarily rush to get my engines attention after testing i definintely flush, reflush and oil as quickly as i can after the day to ensure and stop the oxidation process... everybodies different ...but i have one nova with 11 years on the original bearings, a few with 9, and a pair right now with 4 that are just fine... yeah im due a failure or 2 possibly... but it wont be for a rusty worn bearing surface if i can help it.... 9 times outta 10 upon applying pressure to the inner races upon maintainance i will.. feel the bearing tick... or grind... and its on the bench... now.. before the fuel questions arise... I've used Alan elzers fuel and mixing prowess for years and hands down this is it...with ratios of 65/16, to 65/15... and 70/14... bigger engines may be 60/16... so... just a factor... maybe... im sticking with it... Alan mixes what you ask, consistently from jug to jug, and thats just my deal there... idk... ive just seen quick, or premature wear, and bearing failure on red and blue synthethic oils for yrs and im done... i like morgan... anyway... windy post, read the lines as you can... i guess, and idk... but a more direct approach on maintainance really makes the difference at the bearing store for me.... 'luck brother... keep on keepin on.....mike
 
Bob,

In our motors one of the biggest things to watch is the crank pin wear.

This will save you a lot of problems in the future, but you will need a VERY ACCURATE

GAUGE to measure this wear. Frequent bearing changes are necessary the more you

run your engines. Bearings are cheap compared to replacement parts these days, or new

motors. The clearances in the bearing race and the sizes of the balls are really most of the

problems with our little bearings in our motors. Greg Settle does a GREAT JOB on these

areas in our little bearings. Once again it requires some special tools to care for them.

I hope the 12's are running well in the new boats this year?

Thanks For The Good Topic,

Mark Sholund
 
There is no chrome of any kind that could be applied to steel bearing races or steel bearing balls. Through hardening bearing steels that could be used would include AISI 52100, M-50, # 416 stainless steel.

Jim Allen
 
Thanks Jim,

So the idea that chrome bits come off can't be correct because there is no chrome on them - just shinny stainless steel? Is that what you mean?
 
Mike, that is some good info. I have recently gone back to higher oil content with a significant percentage of castor. I started using all synthetic last year and have had a lot of failures...lesson learned!
 
Thanks Jim,

So the idea that chrome bits come off can't be correct because there is no chrome on them - just shinny stainless steel? Is that what you mean?
Bob,

The first two alloys mentioned are not stainless steels. AISI 52100 is a high carbon, chromium, low alloy steel with a very good through hardening characteristic that is used in most bearing races & balls available on the open market. M-50 is commonly used in high temperature operating situations such as would be found in a turbine. 416 & 440 C are stainless steels that could be used in ball bearing applications. 440 C is capable of attaining the highest strength, hardness & wear resistance, after heat treatment of all the stainless steels alloys. Its very high carbon content is responsible for theses characteristics & makes it well suited for ball bearing applications.

There appears to be some RPM & wear resistance advantages in using AISI 52100 bearings with polished, lapped races & grade 3 ceramic balls. However, none of the previously mentioned materials could be identified by a visual inspection!

JA
 
Bob.. Ceramics... easily...14/2... (16)... 13/2... and yadda... Everybody is different.. i like oil... Id had Gregs bearings in early series novas and the difference was there... i havent talked with nor dealt with him in years..( my friend and early engine builder exited the hobby). i do know... possibly the crank and case went with for fitting/rating and it really wasnt over costly then... and say if you really wanted every edge you could seek... the one thing.. the reeally bad one thing was an over rev... whether it was rough water, or dumbly having a smaller propellor that shouldnt probably been tested anyway... i fractured a ball and it was over... always castor... always... other than that... and now OEM replacement metals work just fine... i think... the new DD 21 nova may have a rear ceramic?.. anyway... choose accordingly, install correctly, and youll be good to go brother... 'luck.... mike...
 
The balls are not stainless and there not chrome they are heat treat

Steel the are what we call Rockwell hard and they are polished to a mirror

Finish when the bearing starts to fail tiny particles of the balls start to collect on the filament wire which causes it to burn out
 
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